George Jamison, Charing Cross, London, England, c. 1800. Movement net
18"h x 8"diameter, overall with base 22"h x 10.5"diameter.
Two plane anchor escapement with divided lift, i.e. the two pallets are in
different planes relative to each other. One half second pendulum with
engraved silvered Earth globe as the bob. Rack and
pinion striking on the hour. Two train chain fusee, with Harrison
maintaining power, eight day duration. Silvered chapter rings and fire gilt
ormolu decorations and
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The apex clock dial displays Greenwich time with along with a perpetual calendar, moon's phase,
and age. Longitude
is indicated by two equatorial bands shown against twenty seven locations of
the world with Greenwich at zero degrees. Local time is read off the two rotating,
silvered rings for minutes and hours and can be set for any location using
the starburst indicator. A zenith ring bearing the four compass points
encircle the device in a vertical plane. This is one of very few examples of
a clock using annular rings to tell the time of English origin. The French
had made more use of this device although usually in a simpler format. The
use of a classical tripod was favored in tellurian and orrery demonstration
models about this time most notably by George Adams, Jr., but this
might be the first example of the use of a tripod to support clockwork.
Thomas Cole is known for using this as a decorative device in his clocks in the mid 1800's.
Albert Odmark, whose collection this example came from noted: "Whilst
English spherical skeleton clocks are extremely rare French examples,
sometimes called horloges á circle de tournants, were made either
at the end of the 18th or very beginning of the 19th Century. They all have
the same two-plane escapement with divided lift (obviating the use of a
verge escapement) horizontal revolving chapter rings and folding tripod
feet. The most complex and there are possibly three examples, are those with
calendar work and of those it is thought that this example with perpetual
calendar, Halifax moon and Greenwich Mean Time is probably the most complex
of all." Two
other simpler examples are depicted here.
Anyone with information about other additional examples please do contact me.
The movement in this clock is oriented in a horizontal plane as opposed
to the conventional arrangement of most clocks that are in a vertical plane.
Before the advent of the pendulum being applied to the anchor escapement in
1666 the verge escapement was the only arrangement for the pendulum. In this
application the crown wheel was in the horizontal plane. Given the geometry
of this clock's movement the use of the verge would have been a logical
choice. However, that escapement has many mechanical disadvantages when it
comes to accurate timekeeping. By the time this clock was conceived the
verge would have been thought to have been hopelessly outdated. So the maker
tried to bring the advantages of an updated escapement to replace the
horizontally oriented crown wheel found in the verge escapement. In this
clock the two train, two-plane anchor escapement takes the place of the
horizontal crown wheel by replacing it with a horizontal anchor wheel. The
pallets for the anchor escapement are normally in the same plane as the
escape wheel, but given that the escape wheel is horizontally positioned and
the pendulum is swinging in the vertical plane this is impossible. Therefore
the the escapement anchor is turned 90 degrees to the escape wheel. This is
not a simple procedure. Both the escape wheel as well is the anchor
escapement must be altered in a custom manner for this arrangement to work,
hence the two plane geometry of the escapement anchor. Also the teeth of the
escape wheel resemble more those of a turbine fan blade in that
they are canted to allow for impulse of the escapement. I have not seen this
type of escapement elsewhere although I'm sure it exists (other than in
these spherical clock examples).
This clock is illustrated in British Skeleton Clocks,
Derek Roberts, pp. 15, 18-19, 22; and Skeleton Clocks,
F.B. Royer-Collard, pp. 100, 102-104.
Provenance: Carter-Wright, 2014.
Formerly Albert Odmark collection, Christie's, London,
Formerly Malcom Gardner, October 20, 1965. Formerly Charles Alix collection,
Seven Oaks, Kent, England.